Known designs of ball bearings that are designed to effect longitudinal movement include return channels for unloaded balls. These return channels are in most cases constructed as bores with square or circular cross-sectional configurations. In the case of return channels with circular cross-sectional configurations, the bore diameter is slightly larger than the diameter of the unloaded balls. Because the unloaded balls in the return tracks are not in contact with the shaft, they are not moved in a forcibly guided manner, but rather are pushed along by the balls leaving the load-bearing zones. When the unloaded balls are pushed through the return channels, the unloaded balls are able to move slightly to all sides because of the larger diameter or width of these return channels. Offset torques that act on the balls are thus created and result in a sliding friction with each other in the contact points of the individual balls. The balls therefore slide through the return channel. These known square or circular return tracks furthermore have little space that is suitable for storing lubricant for the balls.
DE-PS 19 31 983 describes a ball bearing for effecting longitudinal movements that includes an outer bushing with a prismatic inside and a cage. In this ball bearing, the unloaded balls are allowed to move in a groove integrated in one of the prism surfaces and merging tangentially into the other one. This known design also suffers from the disadvantage that it is not able to prevent the sliding of the unloaded balls in the return channel.
In light of the foregoing, a need exists for a longitudinal movement ball bearing that is able to prevent the unloaded balls from sliding in the guide tracks.
A need also exists for a longitudinal movement ball bearing that has sufficient room for storing lubricant.